It is well known that elemental sulfur in hydrocarbon streams, such as petroleum streams, is corrosive and damaging to metal equipment. Elemental sulfur and sulfur compounds may be present in varying concentrations in refined petroleum streams, such as in gasoline boiling range streams. Additional contamination will typically take place as a consequence of transporting the refined stream through pipelines that contain sulfur contaminants remaining in the pipeline from the transportation of sour hydrocarbon streams, such as petroleum crudes. The sulfur also has a particularly corrosive effect on equipment, such as brass valves, gauges and in-tank fuel pump copper commutators.
Various techniques have been reported for removing elemental sulfur from petroleum streams. For example, U.S. Pat. No. 4,149,966 discloses a method for removing elemental sulfur from refined hydrocarbon fuel streams by adding an organo-mercaptan compound plus a copper compound capable of forming a soluble complex with the mercaptan and sulfur. The fuel is contacted with an adsorbent material to remove the resulting copper complex and substantially all the elemental sulfur.
U.S. Pat. No. 4,011,882 discloses a method for reducing sulfur contamination of refined hydrocarbon fluids transported in a pipeline for the transportation of sweet and sour hydrocarbon fluids by washing the pipeline with a wash solution containing a mixture of light and heavy amines, a corrosion inhibitor, a surfactant and an alkanol containing from 1 to 6 carbon atoms.
U.S. Pat. No. 5,618,408 teaches a method for reducing the amount of sulfur and other sulfur contaminants picked-up by refined hydrocarbon products, such as gasoline and distillate fuels, that are pipelined in a pipeline used to transport heavier sour hydrocarbon streams. The method involves controlling the level of dissolved oxygen in the refined hydrocarbon stream that is to be pipelined.
The removal of elemental sulfur from pipelined fuels is also addressed in U.S. Pat. No. 5,250,181 which teaches the use of an aqueous solution containing a caustic, an aliphatic mercaptan, and optionally a sulfide to produce an aqueous layer containing metal polysulfides and a clear fluid layer having a reduced elemental sulfur level. U.S. Pat. No. 5,199,978 teaches the use of an inorganic caustic material, an alkyl alcohol, and an organo mercaptan, or sulfide compound, capable of reacting with sulfur to form a fluid-insoluble polysulfide salt reaction product at ambient temperatures.
Also, U.S. Pat. No. 5,160,045 teaches that the addition of a sulphide to an alkali solution can remove elemental sulfur from hydrocarbon fluids and U.S. Pat. No. 5,250,180 teaches that the addition of an aliphatic mercaptan and a sulphide to an alkali solution can remove elemental sulfur from hydrocarbon fluids. U.S. Pat. No. 5,674,378 teaches the removal of sulfur from a pipelined petroleum stream by contacting the stream with an immiscible treatment comprising water or an immiscible alcohol, caustic, a sulfide or hydrosulfide, and optionally a mercaptan. These components are mixed in a co-current mixer.
U.S. Pat. No. 2,460,227 teaches that the addition of Na2S and an aromatic mercaptan at relatively high concentrations to an alkali solution can remove elemental sulfur from hydrocarbon fluids. However, none of these patents teach the reduction of total sulfur in the hydrocarbon stream while also reducing the elemental sulfur content. In fact, the addition of a sulfur containing species, such as a mercaptan, to the feed under certain conditions results in an increase in total sulfur in the product stream.
While such methods have met with varying degrees of success, there still exists a need in the art for a method capable of reducing the total sulfur content of a hydrocarbon stream while reducing the elemental sulfur content as well.